Immersion responsive sensor

ABSTRACT

The immersion responsive sensor of an automatically inflatable life jacket comprises concentric inner and outer tubular electrodes, the outer one having water access apertures at zones spaced axially from the ends of the inner one. The outer one comprises part of a housing that encloses a battery. Seal means extend across the outer electrode in axially spaced relation to the inner one and have frustoconical inner surfaces that drain water toward the apertures.

' United States Patent Karl-gosta Liedberg inventor Linkoping, Sweden Appl. No. 882,645 Filed Dec. 5,1969 Patented Aug. 31, 1971 Assignee Saab-Scania Aktiebolag Linkoplng, Sweden Priority Dec. 9, 1968 Sweden IMMERSION RESPONSIVE SENSOR 4 Claims, 4 Drawing Figs.

US. Cl..'

Int. Cl

Field of Search ZOO/61.05 H0lh 29/00 ZOO/61.04,

F'Iiiii [56] References Cited UNITED STATES PATENTS 2,812,976 12/1957 Hasenkamp 340/235 X 3,077,288 2/l963 Henry 222/5 Primary Examiner Robert K. Schaefer Assistant ExaminerM. Ginsburg Allpmey-lra Milton Jones ABSTRACT: The immersion responsive sensor of an automatically inflatable life jacket comprises concentric inner and outer tubular electrodes, the outer one having water access apertures at zones spaced axiallyvfrom the ends of the inner one. The outer one comprises part of a housing that encloses a battery. Seal means extend across the outer electrode in axially spaced relation to the inner one and have frustoconical inner surfaces that drain water toward the apertures.

IMMERSION RESPONSIVE SENSOR This invention relates to immersion responsive means for automatically initiating inflation of a life jacket or the like, and is more particularly concerned with an improved immersion responsive sensor for completing a circuit that energizes an electrical actuator when the sensor is immersed in water.

Aviators, sailors and others whose work or recreation subjects them to the risk of immersion in a body of water have need for personal flotation gear, such as a life jacket, which is normally in a compact and unobtrusive condition so that it does not interfere with the wearers activities at times when it is not performing its emergency function, but which can be inflated very quickly when the wearer falls into water. To meet this need, inflatable life jacketshave come into widespread use. Such a life jacket comprises a small bottle of compressed gas and a mechanism for quickly releasing the gas into the inflatable body of the life jacket. r

With many such jackets it is necessary that the wearer manually actuate a part on the gas release mechanism in order to initiate inflation of the jacket, but since the wearer may be unconscious or seriously disabled at the time of his entry into water, increasing attention is being given to the provision of means for automatically effecting inflation of a life jacket in response to its immersion. In general an automatic inflation device comprises a sensor which cooperates with an amplifier or switching device and which responds to the presence of water by causing current to flow from a battery to an electrical igniter for a squib or small cartridge. When the igniter is thus energized, the squib explodes and drives a punch through a seal on the compressed gas bottle, thereby releasing gas from the bottle to permit it to inflate the life jacket.

The immersion responsive sensor is of course a critical part of the automatic inflation apparatus. Unless it functions reliably in an emergency, the jacket may not inflate. and the wearer may lose his life. On the other hand, if the sensor initiates inflation at a time when it should not do so, as in the presence of rain or salt water spray, the inflated jacket may so impede the wearer's activities that its very presence endangers his safety.

In general the sensor comprises a pair of spaced-apart electrodes that are connected in an electrical circuit comprising the battery and the switch or amplifier. When the sensor is immersed, water provides a conductive path between the electrodes, permitting a small control current to flow in the electric circuit. By means of the amplifier or switch, a larger energizing current is then caused to flow in a circuit comprising the battery and the squib igniter or other electrical actuator, thus triggering off the short sequence of events that leads to inflation of the life jacket. When the sensor is not immersed in water, the space between the electrodes of the sensor is relied upon to afford such a high resistance in the circuit comprising the battery and the amplifier that the current flowing therein is at most so small as to be negligible.

In fact, the sensor for an automatically inflatable life jacket has a tendency not to afford a clear-cut on-or-off type of response. When the sensor is immersed, the current through it must be high enough to initiate ignition of the squib, regardless of whether it is immersed in salt water, which is a relatively good conductor of current, or in fresh water which conducts-current rather poorly. When not immersed, the sensor should preferably have an effectively infinite resistance, so

that no drainage of the bat tery takes place even over extended periods of time. Furthermore, the sensor should have such practically infinite resistance even when it is subjected to conditions of extreme atmospheric humidity, and to rain, fog and salt spray, for otherwise it can cause an unexpected and undesired inflation of the life jacket.

Not only must the sensor be able to discriminate between immersion in fresh water and mere exposure to salt spray, but when the apparatus produces an output that initiates life jacket inflation, it must be such an output as will insure ignition of the squib, irrespective of the response current value of the particular squib. Squibs commonly used for life jacket inflation devices vary widely in their ignition current requirements. The minimum current required for ignition of one squib may be as much as twice as high as the minimum current needed for ignition of another. Therefore the only sure way to effect ignition of a particular squib is to supply its igniter with a current no lower than is adequate to fire a squib having the highest minimum ignition current requirement.

In sum, therefore, an automatic inflation initiating device for a life jacket must be capable of a rather close discrimination with respect to the conditions of its environment, but it must either permit no current flow or, when its sensor is immersed, it must cause enough current to flow to the squib igniter to fire a squib having the highest expectable ignition temperature.

With these considerations in mind, it is the general object of this invention to provide an immersion responsive device for initiating automatic inflation of a life jacket or the like, having a sensor which allows no current to flow in its electrical circuits at-times when the sensor is not immersed, even under conditions of high humidity including rain and salt spray, but which, when its sensor is immersed in either salt water or fresh water, provides a high enough ignition current flow to fire any acceptable squib.

Another and more specific object of this invention is to provide an immersion responsive sensor which tends to rid itself of any accumulation of water that develops from causes other than immersion, such as rain, fog and spray; and which, moreover, responds only to the presence 'of a coherent body of water between the sensor electrodes, as distinguished from a film of water or mere drops, but which nevertheless does not require complete and total immersion in water to cause inflation to be initiated.

It is also an object of this invention to provide an automatic immersion responsive inflation initiating mechanism of the character described which is very compact and light in'weight, which carries its battery in a sealed compartment protected from moisture and humidity, even during immersion, and which has a sensor that is protected from airborne moisture such as rain, fog and spray, but which water is readily accessible upon actual immersion.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that such changes in the precise method of practicing the invention' and in the specific apparatus disclosed herein may be made as come within the scope of the appended claims.

The accompanying drawings illustrate two complete exam- 7 ples of embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

F 1G. 1 is a front view of a life jacket embodying the principles of this invention, shown being worn and in its normal uninflated condition;

HO. 2 is a vertical sectional view of the inflating and inflation initiating mechanism of the life jacket;

FIG. 3 is a diagram ofthe electrical circuit ofthe immersion responsive inflation initiating mechanism; and

FIG. 4 is an enlarged detail view of a modified embodiment of the sensor,shown partly in side elevation and partly in section.

Referring now to the accompanying drawings, the numeral S designates generally an inflatable life vest or life jacket embodying the principles of this invention, which is generally U- shaped to have its bight portion around the back of the wearer's neck and its leg portions extending downwardly and overlying his chest. A strap 6 extending transversely to the leg portions of the jacket and secured to them near their lower free ends is fastened around the wearer's waist to secure the device to him.

In its normal uninflated condition, shown in FIG. 1, the life jacket is folded to a substantially flat condition, close to the wearer's body, and it therefore offers little or no interference to bodily movements. When inflated, it distends to a condition in which it can bouyantly support the upper portion of the wearerbody and keep his head out of water.

As is generally conventional, the jacket comprises an outer tubelike envelope of fabric which encloses and protects an inflatable bladder. A zipper 7 on the envelope, extending lengthwise all around it, can be opened for ready access to the bladder. V

The activating mechanism for the jacket is carried in a pocket 8 formed in the fabric envelope at one side thereof. A manual inflation control knob 9 hangs down from the mechanism on a short cord 10 to be accessible beneath the pocket for manual initiation of inflation by a downward pull on the knob 9. The device is also capable of effecting automatic inflation of the jacket in consequence of immersion of the mechanism in a body of water.

The activating mechanism in the pocket 8, which is designated generally by 12, is best seen in FIG. 2. It comprises, in general, a body or base casting 14 which supports a pressure gas bottle 15, a puncturing pin 16, an actuating'lever 18, a sensor 19, a battery 20, and electrical circuit means 23 responsive to immersion of the sensor.

The bottle 15, which contains a charge of gas (e.g., carbon dioxide) under high pressure, is secured to the base casting 14 with its mouth downward and opening to one end of a generally U-shaped passage 21 in the base casting. The mouth of the bottle is normally sealed by a frangible diaphragm that is intended to be ruptured, for jacket inflation, by the puncturing pin 16, which is arranged to slide up and down in the upright portion of the U-shaped passage 21 that is directly beneath the bottle.

The puncturing pin to is pointed at its upper end and has a shoe at its lower end that engages one arm 25 of the actuating lever 18. The actuating lever is medially fulcrumed on a pivot 26 secured in the casting l4, and it has its other arm 28 engaged by a plunger 29 to which the upper end of the cord 10 is secured. v I

When the plunger 29 is moved downwardly, either by a manual pull on the cord 10 or by operation of the automatic mechanism described hereinafter, it swings the arm 28 of the lever 18 downwardly, and concomitantly swings the arm 25 of said lever upwardly, thereby driving the pin 16 up into rupturing engagement with the diaphragm in the mouth of the bottle. The gas thus released from the bottle flows through the U- shaped passage 21 in the base casting to an outlet nipple 30 that has a sealed connection with the bladder, whence it flows into the bladder to inflate the same.

A feature of the activating mechanism of the invention is a condition indicator that is visible through a small window 31 in the base casting. The condition indicator comprises a rotor 32 which has an axially wide rim 33 extending part way around it and which is mounted for rotation on a pin 34 that is fixed in the base casting. The rotor 32 is biased in one direction of its rotation by means of a small spring 35.

When the puncturing pin 16 is in its normal position, it ongages a noncircular peripheral portion of the rotor 32 to confine the rotor against turning in response to the bias of the spring 35. and at such times a green colored area on the rim 33 of the rotor is in register with the window 31 to provide a visible indication that the mechanism is safely available for use.

'When the puncturing pin is raised into rupturing engagement with the diaphragm, it releases the rotor 32 for spring propelled rotation through a predetermined fraction of a turn, by which a red colored area on the rotor rim 33 is brought into register with the window 31', to signify that the bottle has been discharged and should be replaced before the life jacket is used.

Seated in the base casting just above the plunger 29 is an explosive squib 37 that is fired for automatic inflation. When the sensor 19 is immersed in water, current is caused to flow from the battery 20 to an igniter for the squib. The pressure gases generatedby the squib when it is thus fired drive the plunger 29 downward and thus effect rupturing of the gas bottle diaphragm.

The battery 20 and the electrical circuit means 23 are enclosed in an elongated cylindrical housing member 40 which also comprises a part of the sensor 19. The housing member 40 is an upright, axially elongated shell having a generally cylindrical sidewall 41 and an end wall 42 at its top. At its bottom the cylindrical sidewall 41 of the housing member surrounds a headset, 39 on the base casting in which the squib is received, and it has a sealing engagement with the casting. Just above the squib there is a compartment in the housing member in which are located the electrical circuit means '23.

The battery 20 (which can be of the nickel-cadmium type or a similar type having a long shelf acute is enclosed in the upper end portion of the housing member with one of its terminals engaging the end wall 42 to make an electrical connection therewith, said end wall preferably having a central downwardly depressed dimple, as at 43, to insure good contact with the terminal.

Themedial portion of the housing sidewall 41, between the battery and the electrical circuit means, comprises an outer electrode 46 of the immersion sensor 19. Cooperating with it is an inner tubularelectrode 47 that is rigidly held in concentric relation to the outer one by means of generally upright posts 49 that are secured at their bottoms in one of a pair of electrically insulating seal members 50 and 51. The seal members extend across thehousing member 40 in axially spaced relation to the inner electrode and thus define a sensor compartment in the housing. Each of the seal members is preferably made of a water repellent nonhygroscopic plastic insulating material, such as'nylon or Teflon, and has an inner frustoconical surface 52 that is inclined radially and axially outwardly. Axially inwardly adjacent to the junction of each of these frustoconical surfaces with the outer sensor element 46, the latter has a plurality of holes 53 through which water can enterthe sensor compartment. Note that the frustoconical inner surfaces 52 of the seal members encourage rapid drainage of water out of the sensor compartment, through the holes 53, regardless of the orientation of the housing member 40, thus preventing any accumulation of condensate water or the like that might bridge the electrodes. The holes 53 are located in zones spaced axially outwardly from the ends of the inner electrode so that the latter does not interfere with such drainage.

The posts 49 that support the inner electrode 47 are disposed radially inwardly of the inner electrode and extend generally parallel to its axis. Each post has its lower end rigidly secured in the lower seal member 51 and has an outwardly curved upper end portion which is secured to the inner elec trode, as by soldering or welding, to have a good mechanical and electrical connection therewith. At least one of the posts comprises a conductor which extends through the lower seal member to provide an electrical connection between the inner electrode and the resistor 44 and thyristor 45 that are housed beneath the lower seal member.

Note that the posts 49 are so arranged that any water which might. tend to accumulate on the supporting means for the inner electrode will not be in bridging relation to the two electrodes. Preferably the posts 49 are coated with nylon or Teflon to protect them from corrosion and to discourage accumulations of water in the sensor chamber. 7

As already mentioned, one terminal of the battery 20 is grounded through its engagement with the housing end wall 42. The other battery terminal 48 is connected with the electrical circuit means by means of a rigid conductor 54 that extends coaxially through the sensor compartment. The conductor 54' is insulated from the sensor compartment by tubular tions 50 and '51 and abut one another with a snug sealing engagement so that they protect the conductor from contact with any water that may be in the sensor compartment as well as electrically insulating it. i

To insure a good contact between the conductor 54 and the battery terminal 48, a U-shaped conductive spring contactor 56 is preferably secured to the top of the conductor, above the upper seal member 50, which contactor engages said battery terminal under bias.

It will be apparent that the upper seal member 50 cooperates with the upper end of the housing member 40 to provide a sealed, waterproof compartment in which the battery is protectively housed, and that the lower seal member 51 cooperates with the lower portion of the housing member and with the boss 39 on the body casting to provide another sealed compartment that houses the electrical circuit means 23. in addition, the lower seal member can be provided with a downwardly projecting cylindrical sidewall portion 60 that defines a downwardly opening cavity in which the resistor 44 and thyristor 45 are housed, and this cavity can be filled in whole or in part with a plastic encapsulating material to further protect the electrical circuit means.

Since the sensor responds to the presence of a coherent quantity of water bridging the annular space between the electrodes 46 and 47, its opposing surfaces should be of a material that is a good electrical conductor and is resistant to corrosion. For this reason the inner surface of the outer electrode and the outer surface of the inner one are preferably silver plated. The radial distance between these surfaces should be not less than about 5 millimeters so that they cannot be bridged by drops of water that form on them as the result of condensation or are deposited on them by rain or spray.

The water access holes or ports 53 should not be so large that spray and rain drops that have passed through the fabric of the pocket 8 can readily enter them, but they should be big enough so that water which tries to leave the sensor chamber through ther n is not held by surface tension. As illustrated by FIG. 4, the holes 53 can be formed by deforming localized portions of the housing wall outwardly, to produce corbellings 57 like the teeth of a grater that deflect downwardly flowing water away from the holes. Preferably the lower corbellings are made somewhat larger than the upper ones, in view of the draining action of the holes.

As shown in FIG. 3, the inner electrode 47 of the sensor is connected with the resistor 44 and with the gate of the thyristor 45, while the anode and cathode of the thyristor are connected in a series circuit with the battery 20 and the igniter 58 for the squib.

It is necessary that there be only a small flow of current in the gate circuit of a thyristor in order to trigger the device and permit a relatively large current to flow in its anode-cathode circuit. Once triggered, however, the thyristor remains forwardly conductive until current is diverted from its circuit or the cur-rent source fails, even though current flow ceases in the gate circuit. But until the thyristor is triggered by a gate signal, it blocks current flow through its anode-cathode circuit as effectively as an open switch.

With these characteristics of the thyristor 45 in mind, it will be seen that under normal conditions there will be no current drain whatsoever from the battery 20, and the battery will therefore require only very infrequent attention, depending upon its shelf life or any possible emergency activation of the mechanism. This is because the sensor offers an effectively infinite resistance relative to the battery voltage, so long as the sensor is not immersed in water. Should somehow bridge the sensor electrodes, the inflation mechanism will not be triggered by it, inasmuch as the very tiny current flow through such a small volume of water will not attain the critical gate signal value at which the thyristor is rendered forwardly conductive.

However, when the sensor is actually immersed in water,

water will quickly enter through the holes 53 and fill the annu lar space between the electrodes 46.: and 47, soon providing a a drop or two of water' sufficiently low-resistance current conducting path between 7 them to provide for a flow of gate circuit current that is of the critical triggering value.

Since the opposing surfaces of the inner and outer electrodes have substantial area, the space between them need not be completely filled with water for the current flow through such water to reach the critical value. This fact permits the sensor to respond to immersion in either salt water or fresh water, inasmuch as fresh water must attain a somewhat higher level in the sensor chamber than salt water in order to effect triggering of the thyristor.

From the foregoing description taken with the accompanying drawings it will be apparent that this invention provides an automatic inflation mechanism for a life jacket or the like that has a very reliable sensor, not affected by rain, atmospheric humidity or even salt water spray, but which initiates inflation of the life jacket promptly upon being immersed in either fresh water or salt water, and which causes no drain on the battery that energizes the device until actual immersion occurs.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

This invention is defined by the following claims:

1. Means responsive to immersion in water to complete a circuit through which an electrical device such as a squib ig niter is energized from a battery-to effect actuation of emergency equipment, said immersion responsive means comprismg:

A. an elongated substantially tubular outer member I. having an end portion that comprises a battery chamber in which the battery is receivable and 2. having an intermediate portion between its ends that has an electrically conductive inner surface which provides one of a pair of electrodes for electrical connection by water, said intermediate portion being apertured in zones near its ends to provide for entry of water thereinto;

B. sealing means including sealing wall members of electrically insulating material spanning said tubular member and sealed thereto all around it at the ends of said intermediate portion, axially outwardly adjacent to each of said apertured zones, one of said sealing wall members cooperating with said end portion of the tubular member in defining the battery chamber; and

C. a rigid inner member, means whereby said rigid member is supported by one of said sealing wall members in substantially coaxial radially inwardly spaced relationship to the intermediate portion of the outer tubular member and which extends through a substantial portion of the length of said intermediate portion, said inner member having an electrically conductive outer surface which provides the other of said pair of electrodes.

2. The immersion responsive means of claim 1, further characterized by:

each of said sealing wall members having an axially inner surface which is inclined laterally and axially outwardly from the axis of the outer tubular member, to encourage any water in said intermediate portion to drain out of the same through its apertured end zones. 7 3. The immersion responsive "1556? claim 1 further characterized by:

the opposite end portion of the outer tubular member cooperating with the other sealing member to define another chamber for housing electrical instrumentalities for connection with the battery and with said inner and outermenibe rs and the electrical device. I a

4. The immersion responsive means of claim 3, wherein said inner member is tubular, further characterized by:

A. said sealing means including a tubular electrical insulating element extending coaxially through said intermediate. portion of the tubularouter-member, within said wall - other end with said electrical instrumentalities.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECT-ION Patent No. 3 ,602,66l Dated August 31, 1971 Inventor(s) Karl 6.65133 L edberg It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shovm below:

Column 3 line 6 (Specification page 8 line 7) wearer should read -V--wear-er's-- Column 3 line 36 (Specification Page 9 line 7) Change "to" to --l6-- Column 3 line 52 (Specification Page 10 line 5) "of the invention" should read --of this invention-- Column u line 11 (Specification a e 11 line 16) "headset" should read --boss-- Signed and sealed this lhth day of March 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Actesting Officer- Commissioner' of Patents RM po'mso (0459) uscomm-oc GOS'IS-PSQ 9 U,. GOVERNMENT PRNTING OFFICE 9.9 0-356-334 

1. Means responsive to immersion in water to complete a circuit through which an electrical device such as a squib igniter is energized from a battery to effect actuation of emergency equipment, said immersion responsive means comprising: A. an elongated substantially tubular outer member
 1. having an end portion that comprises a battery chamber in which the battery is receivable and
 2. having an intermediate portion between its ends that has an electrically conductive inner surface which provides one of a pair of electrodes for electrical connection by water, said intermediate portion being apertured in zones near its ends to provide for entry of water thereinto; B. sealing means including sealing wall members of electrically insulating material spanning said tubular member and sealed thereto all around it at the ends of said intermediate portion, axially outwardly adjacent to each of said apertured zones, one of said sealing wall members cooperating with said end portion of the tubular member in defining the battery chamber; and C. a rigid inner member, means whereby said rigid member is supported by one of said sealing wall members in substantially coaxial radially inwardly spaced relationship to the intermediate portion of the outer tubular member and which extends through a substantial portion of the length of said intermediate portion, said inner member having an electrically conductive outer surface which provides the other of said pair of electrodes.
 2. having an intermediate portion between its ends that has an electrically conductive inner surface which provides one of a pair of electrodes for electrical connection by water, said intermediate portion being apertured in zones near its ends to provide for entry of water thereinto; B. sealing means including sealing wall members of electrically insulating material spanning said tubular member and sealed thereto all around it at the ends of said intermediate portion, axially outwardly adjacent to each of said apertured zones, one of said sealing wall members cooperating with said end portion of the tubular member in defining the battery chamber; and C. a rigid inner member, means whereby said rigid member is supported by one of said sealing wall members in substantially coaxial radially inwardly spaced relationship to the intermediate portion of the outer tubular member and which extends through a substantial portion of the length of said intermediate portion, said inner member having an electrically conductive outer surface which provides the other of said pair of electrodes.
 2. The immersion responsive means of claim 1, further characterized by: each of said sealing wall members having an axially inner surface which is inclined laterally and axially outwardly from the axis of the outer tubular member, to encourage any water in said intermediate portion to drain out of the same through its apertured end zones.
 3. The immersion responsive means of claim 1, further characterized by: the opposite end portion of the outer tubular member cooperating with the other sealing member to define another chamber for housing electrical instrumentalities for connection with the battery and with said inner and outer members and the electrical device.
 4. The immersion responsive means of claim 3, wherein said inner member is tubular, further characterized by: A. said sealing means including a tubular electrical insulating element extending coaxially through said intermediate portion of the tubular outer member, within said inner member, from one to the other of the sealing wall members and in sealing relation with them; and B. an elongated electrical conductor extending through said insulating element and the wall members for connection at one end with one terminal of the battery and at its other end with said electrical instrumentalities. 